Terminology Rework

Terminology renaming (UI  only): 

* Duck -> Handle
* Curves Panel -> Graphs Panel
* Encapsulate -> Group (icon is reworked accordingly)
* Paste Canvas layer -> Group layer (icon is reworked accordingly)
* Group -> Set (icon is reworked accordingly)
* Add/remove from Group->Add/remove from Set (icons is reworked accordingly)
* BLine -> Spline
* BLine Point -> Spline Point
* BLine Tool -> Spline Tool
* Params Panel -> Parameters Panel
* Children Panel -> Library Panel
* CPoint -> Color stop